Field of the Invention
The present invention relates to an image sensor, a control method for the same, and an image capture apparatus, and more particularly to an image sensor capable of acquiring signals to be used in performing focus detection with a phase difference detection method, and a drive method for the same.
Description of the Related Art
Japanese Patent Laid-Open No. 2001-083407 discloses an apparatus that performs focus detection with a pupil division method, using an image sensor having a micro lens formed in each of pixels that are disposed two-dimensionally. In this apparatus, a photoelectric conversion portion of each pixel is divided into two regions that receive, via the micro lens, light beams that have passed through different regions of an exit pupil of a taking lens. An A image and a B image are respectively generated from the output of the first and second divided regions of a plurality of pixels, and a defocusing amount can be detected, based on a phase difference (shift amount) of the A image and the B image. Also, a normal image signal can be obtained by combining the output of the first divided region and the second divided region on a pixel-by-pixel basis.
In the case of reading out signals from an image sensor having such a configuration, twice the readout time is required when reading out by divided region than in the case of reading out one signal per pixel. Thus, Japanese Patent Laid-Open No. 2013-106194 proposes a technology for reading out the signal of the first divided region first after reading out a reset signal, and then combining the signal of the second divided region with the signal of the first divided region and reading out the combined output. Although a reset signal needs to be read out therebefore, reading out of a reset signal is, in the case of reading out the signal of the second divided region, rendered unnecessary by reading out the combined output, enabling the readout time to be shortened. The signal of the second divided region can be obtained by subtracting the signal of the first divided region from the combined output.
The method of Japanese Patent Laid-Open No. 2013-106194 enables a reduction in the number of times that a reset signal is read out, although since two signals are read out for one pixel, more time is still required than in the case of reading out one signal per pixel, and further shortening of the readout time is desired.